.\"  Copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de)
.\"
.\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
.\" Distributed under GPL
.\" %%%LICENSE_END
.\"
.\"  based on glibc infopages
.\" polished - aeb
.\"
.TH SETNETGRENT 3 2021-03-22 "GNU" "Linux Programmer's Manual"
.SH NAME
setnetgrent, endnetgrent, getnetgrent, getnetgrent_r, innetgr \-
handle network group entries
.SH SYNOPSIS
.nf
.B #include <netdb.h>
.PP
.BI "int setnetgrent(const char *" netgroup );
.B "void endnetgrent(void);"
.PP
.BI "int getnetgrent(char **restrict " host ,
.BI "            char **restrict " user ", char **restrict " domain );
.BI "int getnetgrent_r(char **restrict " host ,
.BI "            char **restrict " user ", char **restrict " domain ,
.BI "            char *restrict " buf ", size_t " buflen );
.PP
.BI "int innetgr(const char *" netgroup ", const char *" host ,
.BI "            const char *" user ", const char *" domain );
.fi
.PP
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.ad l
.PP
.nh
.BR setnetgrent (),
.BR endnetgrent (),
.BR getnetgrent (),
.BR getnetgrent_r (),
.BR innetgr ():
.hy
.nf
    Since glibc 2.19:
        _DEFAULT_SOURCE
    Glibc 2.19 and earlier:
        _BSD_SOURCE || _SVID_SOURCE
.fi
.ad
.SH DESCRIPTION
The
.I netgroup
is a SunOS invention.
A netgroup database is a list of string triples
.RI ( hostname ", " username ", " domainname )
or other netgroup names.
Any of the elements in a triple can be empty,
which means that anything matches.
The functions described here allow access to the netgroup databases.
The file
.I /etc/nsswitch.conf
defines what database is searched.
.PP
The
.BR setnetgrent ()
call defines the netgroup that will be searched by subsequent
.BR getnetgrent ()
calls.
The
.BR getnetgrent ()
function retrieves the next netgroup entry, and returns pointers in
.IR host ,
.IR user ,
.IR domain .
A null pointer means that the corresponding entry matches any string.
The pointers are valid only as long as there is no call to other
netgroup-related functions.
To avoid this problem you can use the GNU function
.BR getnetgrent_r ()
that stores the strings in the supplied buffer.
To free all allocated buffers use
.BR endnetgrent ().
.PP
In most cases you want to check only if the triplet
.RI ( hostname ", " username ", " domainname )
is a member of a netgroup.
The function
.BR innetgr ()
can be used for this without calling the above three functions.
Again, a null pointer is a wildcard and matches any string.
The function is thread-safe.
.SH RETURN VALUE
These functions return 1 on success and 0 for failure.
.SH FILES
.I /etc/netgroup
.br
.I /etc/nsswitch.conf
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lb lb lbx
l l l.
Interface	Attribute	Value
T{
.BR setnetgrent (),
.BR getnetgrent_r (),
.BR innetgr ()
T}	Thread safety	T{
MT-Unsafe race:netgrent
locale
T}
T{
.BR endnetgrent ()
T}	Thread safety	T{
MT-Unsafe race:netgrent
T}
T{
.BR getnetgrent ()
T}	Thread safety	T{
MT-Unsafe race:netgrent
race:netgrentbuf locale
T}
.TE
.hy
.ad
.sp 1
In the above table,
.I netgrent
in
.I race:netgrent
signifies that if any of the functions
.BR setnetgrent (),
.BR getnetgrent_r (),
.BR innetgr (),
.BR getnetgrent (),
or
.BR endnetgrent ()
are used in parallel in different threads of a program,
then data races could occur.
.SH CONFORMING TO
These functions are not in POSIX.1, but
.BR setnetgrent (),
.BR endnetgrent (),
.BR getnetgrent (),
and
.BR innetgr ()
are available on most UNIX systems.
.BR getnetgrent_r ()
is not widely available on other systems.
.\" getnetgrent_r() is on Solaris 8 and AIX 5.1, but not the BSDs.
.SH NOTES
In the BSD implementation,
.BR setnetgrent ()
returns void.
.SH SEE ALSO
.BR sethostent (3),
.BR setprotoent (3),
.BR setservent (3)
